Night vision systems operate to greatly enhance low levels of ambient, or externally provided illumination and permit a user to make observations and carry on activities under conditions of near total darkness. In some instances, the devices are sensitive to wave lengths of light outside the normal human visual range. One particular utility for night vision equipment is as a sighting device for firearms and such equipment is sold by Kigre, Inc. of Hilton Head, S.C. a under the designation KN-200 and KN-250.
A beam splitter is an important component of many night vision devices. The beam splitter includes a mirror which directs a first portion of an incident light beam to a first channel of an optical system and a second portion to a second channel. In some instances, the mirror is a dichoric mirror which reflects a first group of wavelengths, typically infrared wave lengths, and transmits a second, typically visible, group of wavelengths. In other instances, the beam splitter includes a partially silvered mirror. It will be appreciated that alignment of the elements of any optical system is critical; and this is particularly so when the optical system is used as part of a firearm sighting device. Heretofore, beam splitters of the type employed in combination with night vision devices comprised sealed optical units which included a mirror supported by three adjustment screws. If the beam splitter needed alignment, it had to be returned to a factory service facility for disassembly. Furthermore, the use of three mounting screws for positioning the mirror made alignment difficult.
Beam splitters associated with night vision equipment are typically employed under harsh conditions, and cannot always be readily returned to the factory for realignment. Accordingly, there is a need for a beam splitter, particularly one of the type utilized in conjunction with night vision equipment, which may be easily adjusted in the field without disassembly. Furthermore, this device should be rugged and environmentally sealed.
The present invention provides a field adjustable beam splitter in which the position of the mirror may be simply and accurately adjusted along two mutually perpendicular axes so as to provide true windage and elevation adjustment capabilities. This feature makes the device very compatible with firearm sighting systems. The beam splitter of the present invention is accurate and rugged and permits rapid boresighting of firearms in the field. These and other advantages of the present invention will be readily apparent from the drawings, discussion anti description which follow.